Validation failed for one or more entities. See 'EntityValidationErrors' property for more details

如果使用的是Code First，使用update database -verbose完成了miragtion 之后，运行发现异常：

Validation failed for one or more entities. See ‘EntityValidationErrors‘ property for more details

这是由于migration对model的更改导致了db中column的限制（例如长度，StringLength(30)会导致nvarchar(max)变为nvarchar(30)）

想要看到异常的具体信息，可以catch DbEntityValidationException :

try
{
    // Your code...
    // Could also be before try if you know the exception occurs in SaveChanges

    context.SaveChanges();
}
catch (DbEntityValidationException e)
{
    foreach (var eve in e.EntityValidationErrors)
    {
    }
}

Validation failed for one or more entities. See 'EntityValidationErrors' property for more details

原文：http://blog.csdn.net/lan_liang/article/details/39397269